Tailored magnetic properties of Sm(Zn) substituted nanocrystalline barium hexaferrites

Sm and SmZn substituted nanocrystalline barium hexaferrites (Ba1−xSmxFe12O19 and Ba1−xSmxFe12−xZnxO19, x = 0–0.6) were prepared by the sol–gel autocombustion process. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to characterize the phase composition, crystal structure and magnetic properties of the as-prepared barium hexaferrites. All results indicated that the substitution content (x) critically influenced on the phase composition and magnetic properties. When the substitution content x > 0.2, impurity phases such as α-Fe2O3, SmFeO3 and ZnFe2O4 were detected, which diluted and weakened saturation magnetization (Ms). For the Sm-doped samples, owing to the hyperfine field, canting spin, magnetic dilution and impurity phases, Ms increased with x firstly, and then decreased when x > 0.03. On the other hand, the coercivity (Hc) continuously increased with x. Nevertheless, for the SmZn-doped samples, Ms reached maximum when x = 0.06 and Hc almost unchanged with x. Compared the magnetic properties of Sm- and SmZn-doped samples, it was proved that Zn2+ substituted Fe3+ at 4f2 sites and Sm3+ substituted Ba2+, which changed Fe3+ to Fe2+ at 2a sites in order to satisfy the electroneutrality principle.